title: Salmonella enterica serovar Typhimurium virulence-resistance plasmids derived from the pSLT carrying nonconventional class 1 integrons with dfrA12 gene in their variable region and sul3 in the 3' conserved segment.
abstract: Drug-resistant derivatives of serovar-specific virulence plasmids, such as pSLT, in clinically-relevant Salmonella enterica serovar Typhimurium strains, represent a threat for human health. We have analysed 14 S. Typhimurium isolates recovered in Italy and the United Kingdom from swine and from cases of human infection for the presence of virulence-resistance (VR) plasmids. They were negative for the multidrug resistance (MDR) region of the Salmonella genomic island 1 (SGI1), but expressed resistance to ampicillin, chloramphenicol, streptomycin/spectinomycin, sulfamethoxazole, and tetracyclines. The isolates were characterised by XbaI pulsed-field gel electrophoresis, multilocus sequence typing, and detection of resistance and virulence determinants (PCR/sequencing). Identification of VR plasmids was accomplished by PCR detection of bla genes (encoding ampicillin resistance), class 1 integrons and the pSLT virulence gene spvC. Plasmid analyses were performed by alkaline lysis, S1-nuclease digestion, replicon typing, conjugation, restriction analyses, and Southern blot/hybridization. Two blaOXA-1 positive isolates contained pSLT-derived plasmids related to pUO-StVR2. In nine isolates, eight from swine and one from a patient, MDR-conferring-IncFII-VR plasmids were detected. They contained the blaTEM-1 gene as well as a nonconventional class 1 integron with dfrA12-aadA2 gene cassettes in its variable region, and a sul3 gene in the 3' conserved segment. Restriction analysis suggested a novel pSLT variant. The results obtained underline the role of swine as a potential reservoir for the blaTEM-1-IncFII-plasmids. The occurrence and spread of virulence- and MDR-conferring plasmids should be considered as a potential public health problem.
authors.affiliation: 1 Department of Biological Safety, Federal Institute for Risk Assessment (BfR) , Berlin, Germany .
authors.forename: Janine
authors.initials: J
authors.lastname: Beutlich
authors.forename: M Rosario
authors.initials: MR
authors.lastname: Rodicio
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Mendoza
authors.forename: Patricia
authors.initials: P
authors.lastname: García
authors.forename: Miranda
authors.initials: M
authors.lastname: Kirchner
authors.forename: Ida
authors.initials: I
authors.lastname: Luzzi
authors.forename: Dik
authors.initials: D
authors.lastname: Mevius
authors.forename: John
authors.initials: J
authors.lastname: Threlfall
authors.forename: Reiner
authors.initials: R
authors.lastname: Helmuth
authors.forename: Beatriz
authors.initials: B
authors.lastname: Guerra
mesh_terms: D024509:3' Flanking Region; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D017124:Conserved Sequence; D004197:Disease Reservoirs / Q000382:microbiology / Q000662:veterinary*; D024901:Drug Resistance, Multiple, Bacterial; D005798:Genes, Bacterial; D014644:Genetic Variation; D006801:Humans; D032023:Integrons; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D058885:Multilocus Sequence Typing; D010957:Plasmids; D012481:Salmonella Infections, Animal / Q000188:drug therapy / Q000382:microbiology* / Q000635:transmission; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D013552:Swine; D014774:Virulence
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; C489157:Sul3 protein, Salmonella enterica